It is also used to record the noise of laser shots. From the variations in intensity it is possible to extrapolate information about the structure of rocks on Mars. The recorded sounds will differ depending on the hardness and quality of the mineral hit.
The main difficulty relates to the temperature variations that range from -40°C inside the SuperCam to -120°C outside.
The mic is fitted with cables that have a very special conductor made from manganin to limit heat exchanges as much as possible.
On Mars sound does not travel as it does on Earth, since the pressure is 150 times weaker than terrestrial pressure, and the composition of the atmosphere is very different. The sound level is 20dB lower than in the same situation on Earth.
Mars’ atmosphere transmits sounds poorly, so the project team had to factor in these constraints and make an extremely sensitive microphone. Most of Mars’ atmosphere is made up of carbon dioxide, which absorbs audio frequencies that humans can hear much better than it absorbs infrasound. High frequencies carry less well, so sounds become muted.
In this context, a 50dB sound will be completely muted from as little as 20 or 30 meters away and a high-pitched tone of 20kHz will not make it more than one or two meters.
The Mars Microphone has also been used to listen to the drone helicopter at take-off and landing.
The manufacturing secrets are carefully guarded but persistent rumors suggest it was equipped with a specially designed COSI to resist a temperature of -120° and was used to dull the effects of turbulence caused by wind and the famous dust devils.
When filing the patent for the COSI, Philippe Chenevez, the Cinela boss, surely did not think of extending it to cover the Red Planet.
In his books the writer Edgar Rice Burroughs described little green men who want to seize control of earthlings’ inventions, resulting in an industrial war. Let us hope none of them are sniffing around the Perseverance because they are more dangerous than the crocodiles depicted by the Australian director Peter Faiman in the film Crocodile Dundee.